Amount Of Smear Layer Research Articles

The evaluation of root surface modifications after different subgingival mechanical instrumentation techniques – an in vitro study

Objectives. The aim of this in vitro study was to observe through scanning electron microscopy (SEM) the surface morphology of root samples treated with different mechanical instrumentation methods and the additional application of a nano-colloidal silver-based antiseptic solution. Material and methods. Root samples were prepared from extracted molars and divided in four groups: group 1 of samples was instrumented with Gracey curette (7/8), group 2 of samples was instrumented with ultrasonic tip 1S, group 3 of samples was instrumented with ultrasonic tips 1S plus H4R/L, group 4 of samples was treated with ultrasonic tips 1S plus H4R/L and application of the silver-based antiseptic solution. All samples were then subjected to SEM examination. Outcomes. Group 1 of samples presented a smoother surface compared to the samples in the other groups. Group 2, 3 and 4 displayed superficial grooves parallel to the direction of action of the ultrasonic tip. In group 3 and 4, root planning with tip H4R/L did not ameliorate the smoothness of the surface. The smear layer was present, regardless the instrumentation method. In group 4, the additional application of the antiseptic solution did not influence the surface morphology or the amount of smear layer. Conclusions. Gracey curettes created a smoother radicular surface compared to ultrasonic tips. Smear layer was obvious on the radicular surfaces, no matter the instrumentation method. The application of the silver-based antiseptic solution had no additional impact on surface morphology.

Comparative evaluation of canal cleanliness at apical third using Self-Adjusting File and Wave One File with different irrigants: an in vitro scanning electron microscopic study.

To evaluate the cleaning ability of two single-file rotary systems- Self-Adjusting File (SAF) and Wave one (WO) systems in removing the smear layer using sodium hypochlorite (NaOCl) + ethylene diamine tetraacetic acid (EDTA) and NaOCl + Qmix as irrigants at apical one-third of the root canal. Forty extracted human mandibular premolars were selected and working length was determined. The canal was manually instrumented up to a number 25 size K-file. The roots were divided into the following groups with 10 samples each - Group 1 using SAF: Group 1a- 3% NaOCl + 17% EDTA, Group 1b- 3% NaOCl + Qmix. Group2 using WO: Group 2a- 3% NaOCl + 17% EDTA, Group 2b- 3% NaOCl + Qmix. In the SAF group, the irrigation was performed continuously using the special irrigation apparatus. In the WO group, syringe irrigation was done followed by final irrigant activation using passive ultrasonic irrigation (PUI). The roots were sectioned longitudinally and subjected to scanning electron microscopic (SEM) examination. The amount of smear layer was evaluated using a five score index at the apical third level. Statistical analysis was performed using the Chi-square test. Group 1 (SAF) showed better canal cleanliness at apical third compared to Group 2 (WO) with both irrigant combinations and the results were statistically significant (p<0.05). 3% NaOCl + Qmix was equally as effective as 3% NaOCl + 17% EDTA in removing the smear layer with no significant difference between them. Within the limitation of this study, SAF in combination with 3% NaOCl + Qmix or 3% NaOCl + 17% EDTA should be used for removing smear layer in critical areas of the root canal.

The Evaluation of Debris and Smear Layer Generated by Three Rotary Instruments Neo NiTi, 2Shape and Revo_S: An Ex-vivo Scanning Electron Microscopic Study.

This study compared the cleaning effectiveness of NeoNiTi, 2Shape and Revo_S rotary instruments. Fifty mandibular molar mesial roots were selected with an angle of curvature less than 20 degrees divided into three groups (n=15). Five samples were selected as negative control group. In all three systems, the final file was 25, 6%. The score of debris and smear layer in three thirds (coronal, middle and apical) of the root canal walls were evaluated using scanning electron microscopic (SEM) magnification. The data were analyzed using the Kruskal Wallis and Mann Whitney U tests for intergroup comparison (P≤0.05) and Freidman and Wilcoxon signed-rank test was employed for intragroup comparison (P≤0.05). Residual debris of the 2Shape system in the apical region was significantly higher than the other two systems (P=0.039). Revo_S and 2Shape groups had significantly higher quantities of debris in the apical than the coronal region (P=0.029 and P=0.02, respectively). In the 2Shape group, the amount of mid-region debris was significantly higher (P=0.005) than the coronal. In inter-group comparison there was no significant difference in residual smear layer between the systems. In intra-group comparison in all three systems, the amount of smear layer in the coronal third was significantly higher than in the other two areas. (P=0.017, P<0.001 and P=0.032, respectively). 2Shape left the highest amount of debris in the apical region. The amount of debris in Revo_S and 2Shape groups in the apical region was significantly higher than in the coronal. The amount of smear layer in all three groups in the coronal area was higher than the middle and apical areas.

Effect of Different Final Irrigation Activation Methods on Root Canal Cleanliness

Aim: to evaluate canal cleanliness after using manual dynamic activation, passive ultrasonic irrigation and photoactivated disinfection in comparison with conventional needle irrigation, using scanning electron microscopy Methods: Sixty single rooted human premolars with nearly straight single canal were collected, the crowns of all teeth were removed near the level of cementoenamel junction to obtain approximately 15 ±1 mm uniform root lengths. After instrumentaion with ProTaper Next files up to X4 (40/06), roots were randomly divided into 4 equal groups (n=15) according to the method of final irrigation activation. Group I: Conventional needle and syringe irrigation. Group II: Manual dynamic activation. Group III: passive ultrasonic irrigation. Group IV: photoactivated disinfection. Canal cleanliness was evaluated with SEM using different magnification (X350- X1000). Results: Group III had the best cleanliness of the root canal while Group I had the worst cleanliness, there were statistical significant differences between Group I versus Groups II and III and between Group III and Group IV (P ≤ 0.05). Regardless the irrigation activation method, the coronal level showed significantly less amount of smear layer and remaining debris than the apical level. Conclusions: None of the tested final irrigation activation methods resulted in completely clean canal wall.

Scanning Electron Microscopic and Dye Penetration Evaluation of Hand Instrumentation Techniques on Formation of Smear Layer in Root Canal Preparation: An In vitro Study.

Aims and Objectives:The present study was undertaken for evaluating various hand instrumentation techniques with different instruments in the formation of smear layer.Materials and Methods:One hundred and seventy-five extracted mandibular molars were collected and were cut at cementoenamel junction. Afterward, the distal roots were separated. Working length was determined, and roots were divided into five equal groups with 35 roots in each group as follows: Group A: K-type files with conventional step-back technique, Group B: Canal Master U instrument with clockwise–counterclockwise rotation, Group C: Flex-R® files with clockwise–counterclockwise rotation, Group D: FlexoFiles® with conventional step-back technique, and Group E: Nickel titanium files with conventional step-back technique. Biomechanical preparation was done according to their respective groups. The teeth in various groups were scanned under scanning electron microscope and scoring was done. All the results were analyzed by SPSS software version 17.0.Results:Scanning electron microscopic results indicated that apparently there seems to be a significant difference in the scoring of the smear layer between each group at all the three levels, but the difference was statistically nonsignificant. Microleakage was present in all the samples. Nonsignificant results were obtained while comparing the microleakage in between different the groups. However, microleakage was highest in Group D.Conclusion:The amount of smear layer is maximum at the apical third and lesser in the middle third followed by the coronal third in all the groups. All the samples showed microleakage to a varying extent.

Evaluation of debris and smear layer formation using three different NI-TI rotary instrument systems: An in vitro scanning electron microscope study.

Aim: The aim of the study is to evaluate of debris and smear layer formation after using rotary ProTaper Universal, Twisted File, and XP Endo file systems under scanning electron microscope.Materials and Methods: Forty freshly extracted mandibular second premolar teeth were taken to decoronate at the cementoenamel junction to make the remaining root length 15 mm. Specimens were divided into four groups of 10 teeth each, Group I (control) – no instrumentation. Group II – ProTaper Universal rotary file (F2), Group III – twisted file (ISO size 0.25 and 6% taper), Group IV – XP Endo file (ISO size 0.25). During instrumentation, 5 ml normal saline was used as irrigating agent. Grooves parallel to the longitudinal axis of the root were made on the mesial and distal surface of each specimen to split it into two halves and examined under scanning electron microscope at ×1500 and ×5000 magnification. Photomicrographs were taken to evaluate debris and smear layer. Evaluation of photomicrographs was done using a score index.Results: One-way analysis of variance (ANOVA) was used to compare more than one means at a time. Tukey's critical difference followed by ANOVA was used to compare the mean values pair wise. P <0.05 was considered to be statistically significant. Among all the file systems, Group II showed maximum amount of debris (3.50 ± 1.109) followed by Group III (2.83 ± 1.238) and least amount was showed by Group IV (2.65 ± 1.122) at all levels (cervical, middle, and apical third). Among all the experimental groups, Group II showed maximum amount of smear layer (2.75 ± 1.149) followed by Group III (2.40 ± 0.982) and least amount of smear layer shown by Group IV (2.10 ± 0.841) at all levels (cervical, middle and apical third), the result was statistically significant (P < 0.05).Conclusions:At all the levels (cervical third, middle third, and apical third), among all the experimental groups, highest amount of debris and smear layer was formed by ProTaper Universal rotary file followed by Twisted file and least amount showed by XP Endo file system. In all the levels, control group showed highest amount of debris but least amount of smear layer.

Analysis of the smear layer generated by different activation systems: an in vitro study.

To evaluate via scanning electron microscopy the amount of smear layer generated during the use of sonic and ultrasonic activation systems with standardized short-term intentional contacts with the canal walls. Seventy single-root human teeth were randomly assigned to 2 control (n= 5 each): NC (negative control), PC (positive control) and four experimental groups (n= 15 each): NC (negative control), PC (positive control), G1 (passive ultrasonic irrigation with Irrisafe), G2 (ultrasonic irrigation with EndoUltra), G3 (sonic irrigation with Endoactivator), G4 (sonic irrigation with Eddy). Samples were instrumented with ProTaper Next®. An irrigation protocol with sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) was followed for both PC and the experimental groups. Standardized intentional contacts were made in the mesial walls during 5s at WL - 2mm in all experimental groups. Two calibrated evaluators scored the smear layer generated with an ordinal scale by scanning electron microscopy. The weighted kappa coefficient (Kw) was calculated to determine the inter-observer agreement. Post-consensus ordinal data were analyzed using the ordinal (linear) chi-square test. When the agitation file is in contact with dentine walls, Irrisafe® significantly generated the least amount of smear layer in the coronal third (p< 0.05). Both in the middle and apical third, activation with Irrisafe® also showed statistically significant better results than Eddy™ and EndoUltra®. Endoactivator® showed significant better results than EndoUltra® and Eddy™ in the apical third (p< 0.05). Irrisafe generated the least amount of smear layer in the entire canal and similar to Endoactivator in the apical third when the agitation file is in contact with dentine walls. The smear layer is generated during activation. It is common to apply irrigation protocols where after the removal of the smear layer using chelants, a final rinse and activation is carried out but there are no previous studies analyzing the possible creation of a new smear layer with this final activation.

Cleanliness efficacy and effect on dentin microhardness of a novel plant extract irrigant

ObjectiveThis study was done to evaluate the effect of the prepared Moringa oleifera-based root canal irrigant compared to conventionally used irrigants on the microhardness of root dentin and smear layer removal.Materials and methodsOne hundred freshly extracted teeth with single root were divided into 5 groups according to the irrigant used: group 1, saline; group 2, Moringa oleifera; group 3, Moringa oleifera + chlorhexidine; group 4, chlorhexidine; and group 5, sodium hypochlorite. Root canal preparation was done using Protaper universal system till size F5 using one of the irrigants after each file. Fifty teeth were prepared to measure dentin microhardness, while the remaining fifty were prepared for evaluation of the remaining debris and smear layer using stereomicroscope and scanning electron microscope (SEM) in each third of the canal.ResultsChlorhexidine alone and combined with Moringa oleifera showed higher microhardness values in apical and coronal parts. In the middle parts, chlorhexidine followed by Moringa oleifera showed the highest results. SEM examination showed that none of the used irrigants has the ability to completely remove smear layer. However, Moringa oleifera group showed the least amount of smear layer on canal wall.ConclusionsMoringa oleifera is a promising final irrigant solution alone or combined with chlorhexidine throughout the instrumentation. Moringa oleifera was proved to have a high effect as a chelating agent.

Effectiveness of Nickel-Titanium Endodontic Instruments on Smear Layer Removal from Radicular Dentin. A Scanning Electron Microscopy Study

The aim of our study was to evaluate the cleaning effect of nickel-titanium (Ni-Ti) rotary files on the smear layer formed on the radicular dentine walls during endodontic procedures. We used 50 freshly extracted maxillary permanent teeth divided in two study groups according to the instruments used for cleaning: Group 1 with ProTaper Ni-Ti rotary files, Group 2 with manual Ni-Ti files. Longitudinal sections of root canals from each group were evaluated by scanning electron microscopy (SEM) in the apical, middle and coronal sections. Representative microphotographs were taken and double blind scoring was performed by calibrated examiners. The amount of smear layer was measured according to Hulsmann scoring system and the data were statistically analyzed. There were statistically significant differences between instruments in the apical root canal sections (p[0.05), where the manual Ni-Ti files gave the best cleaning scores. There were no differences between groups for the middle and coronal thirds. In conclusion, the best approach for an effective removal of smear layer is to combine manual files with rotary Ni-Ti instruments during the endodontic treatment.

COMPARISON OF CROSS-SECTION CHANGES AND CLEANING OF CURVED CANALS PREPARED BY DIFFERENT SYSTEMS

Aim: to evaluate the changes in the canal cross sectional area by using cone beam computed tomography (CBCT) and the cleaning ability of root canals by using stereo microscope and scanning electron microscope. Materials and methods: a total of 40 extracted mandibular first molar teeth were collected. The curvature of each mesio-buccal canal in each root was determined according to Schneider’s technique by using cone beam computed tomography and Roots with angles of curvature ranging from 25-45o were selected. The samples were classified into four groups (10 each) according to the preparatory system used in the preparation. Evaluation of change in cross sectional area was done by using Cone beam computed tomography and Evaluation the cleaning ability of root canals was done by using stereo microscope and scanning electron microscope. Results: One-shape and Revo-S Ni-Ti rotary systems produced more changes in the canal cross sectional area at all canal levels than Liberator Ni-Ti rotary system and K-file hand instruments. Regarding smear layer scores, all the tested systems were unable to produce dentin surface free from smear layer: Revo-S and Liberator Ni-Ti rotary systems produced less amount of smear layer than One-shape Ni-Ti rotary system and K-file hand instruments at the apical region. Conclusions: The change in the canal cross sectional area is directly proportional to the amount of debris removal from the canal space with the four tested systems

The smear layer created by scaling and root planing is physiologically eliminated in a biphasic process.

Mechanical instrumentation of the root surface causes the formation of a smear layer, which is a physical barrier that can affect periodontal regeneration. Although different procedures have been proposed to remove the smear layer, there is no information concerning how long the smear layer persists on root surfaces after instrumentation in vivo. This study assessed the presence of the smear layer on root surfaces over a 28-day period after subgingival instrumentation with hand instruments. Fifty human teeth that were referred for extraction because of advanced periodontal disease were scaled and root planed (SRP) by a single experienced operator. Ten teeth were randomly assigned to be extracted 7, 14, 21, and 28 days after SRP. Another 10 teeth were extracted immediately after instrumentation (Day 0, control group). The subgingival area of the instrumented roots was evaluated with scanning electron microscopy. Representative photomicrographs were assessed by a blinded and calibrated examiner according to a scoring system. A rapid and significant (p < 0.05, Z test) initial reduction in the amount of smear layer was observed at 7 days, and a further significant (p < 0.05) decrease was observed 28 days after SRP. Interestingly, even 28 days after SRP, the smear layer was still present on root surfaces. This study showed that the physiological elimination of the smear layer occurred in a biphasic manner: a rapid initial reduction was observed 7 days after instrumentation, which was followed by a slow process leading to a significant decrease 28 days after instrumentation.

Scanning Electron Microscopic Evaluation of Residual Smear Layer Following Preparation of Curved Root Canals Using Hand Instrumentation or Two Engine-Driven Systems.

Introduction:In this experimental study, the amount of smear layer (SL) remnants in curved root canals after chemomechanical instrumentation with two engine-driven systems or hand instrumentation was evaluated. Methods and Materials:Forty-eight mesiobuccal roots of mandibular first molars with curvatures ranging between 25 and 35 degrees (according to Schneider’s method) were divided into three groups (n=16) which were prepared by either the ProTaper Universal file series, Reciproc single file system or hand instrumentation. The canals were intermittently irrigated with 5.25% NaOCl and 17% (ethylenediaminetetraacetic acid) EDTA, followed by distilled water as the final rinse. The roots were split longitudinally and the apical third of the specimens were evaluated under 2500× magnification with a scanning electron microscope (SEM). The mean scores of the SL were calculated and analyzed using the non-parametric Kruskal-Wallis and Mann-Whitney U tests. Results:The mean scores of the SL were 2.00±0.73, 1.94±0.68 and 1.44±0.63 µm for the ProTaper Universal, Reciproc and hand instrumentation, respectively. Mean score of SL was significantly less in the hand instrumentation group than the ProTaper (P=0.027) and Reciproc (P=0.035) groups. The difference between the two engine-driven systems, however, was not significant (P=0.803). Conclusion:The amount of smear layer in the apical third of curved root canals prepared with both engine-driven systems was similar and greater than the hand instrumentation technique. Complete cleanliness was not attained.

An &amp;lt;i&amp;gt;in vitro&amp;lt;/i&amp;gt; study on cleaning efficiency of Mtwo and BioRaCe rotary nickel-titanium instruments

Complete removal of smear layer and debris during the process of root canal therapy is of paramount importance in order to achieve the objectives of endodontic treatment. The aim of this study was to compare the amount of extruded debris and smear layer using two widespread rotary nickel-titanium instruments. Fifty eight freshly extracted human mandibular first molar mesial canals were randomly assigned into two groups. The root canals were instrumented using Mtwo (VDW, Munich, Germany), and BioRaCe (FKG Dentaire, LaChauxde-Fonds, Switzerland) NiTi instruments. Debris and smear layer from the apical thirds part during instrumentation were evaluated by scanning electron microscope. Then, the scores of remaining debris and smear layer were calculated for each group and compared. Data were then statistically analyzed using Mann-Whitney U test. There were significant differences in the amount of smear layer among two groups (P extruded by the BioRaCe group and the least by the Mtwo group. The results of the present study showed that, although both instrumentation techniques apically extruded debris and smear layer through the apical foramen, the Mtwo instruments induced less extruded debris and smear layer than the BioRaCe rotary systems.

Er:YAG 2,940-nm laser fiber in endodontic treatment: a help in removing smear layer

Cleaning and disinfection of the root canal system are some of the most important goals in endodontic therapy. The aim of this preliminary study is to assess the effectiveness of Er:YAG laser fiber in removing the smear layer produced during root canal walls instrumentation. Forty-eight single-rooted teeth were prepared with manual and rotary Ni-Ti instruments, in addition to 2.5% NaOCl irrigation. Samples were randomly subdivided into groups and treated with: three irradiations of 5 s each, with 300-μm Er:YAG endodontic fiber, 1 W and 2.5% NaOCl solution (A Group); two laser irradiations with 17% EDTA solution and 2.5% NaOCl solution (B Group); laser irradiation plus 17% EDTA solution and 2.5% NaOCl (C Group); only in the final wash of 17% EDTA (control group D). During laser treatment, temperature variations were analyzed by using thermocouple and thermal camera devices in order to test both deep and superficial temperatures. Each sample was finally observed by scanning electron microscope (SEM) at the coronal, medium, and apical thirds at ×500 magnification and blindly scored depending on the amount of smear layer. Statistical analysis of the results was conducted using the Kruskal-Wallis and Mann-Whitney test to determine the eventual significant differences between the quantity of smear layer in each group and between the groups at coronal, medium, and apical third: a p value <0.05 was considered significant. The thermal analysis realized by thermocouple with the used parameters demonstrated that laser endodontic fiber produces an average deep temperature increase of 3.5 ± 0.4 °C; analysis performed with a thermal camera showed an average superficial temperature increase of 1.3 ± 0.2 °C produced by laser endodontic fiber use. Deep and superficial temperatures fall immediately after irradiation possibly without causing structural damage or anatomical alteration inside the root canal and neither on periodontal tissues. SEM analysis showed that specimens of group B had the highest level of cleaning in every third, with a significant difference with groups D and A; group C samples showed a good percentage of cleaned tubules in apical and middle thirds, while group D teeth showed open dentinal tubules in coronal third, with a statistical difference with group A samples which were the worst cleaned. The Er:YAG fiber double irradiation with EDTA 17% and NaOCl 2.5% has been demonstrated to be effective in removing smear layer, even in the apical third which is described as the hardest area to clean during endodontic treatment.

The Effect of the NRT Files Instrumentation on the Quality of the Surface of the Root Canal Wall

To analyze in vitro, trough scanning electron microscope (SEM), the shaping ability of NRT NiTi rotary system (Mani, Inc, Toshigi-Ken, Japan). Ten extracted human teeth were cut at the level of the CEJ and prepared with Gates-Glidden burs 4-3-2 and NRT rotary files up to size #35. Irrigation was performed with 7.5 mL of 5% NaOCl and 7.5 mL of 10% EDTA during each canal instrumentation. Following the shaping sequence, a final irrigation was performed with EDTA followed by NaOCl, each left in situ for three minutes. Teeth were then fractured longitudinally, and the coronal, middle, and apical thirds of the canals were inspected with SEM. Three parameters, divided into four different levels (Alfa and Bravo, considered clinically acceptable; Charlie and Delta, considered clinically unacceptable), were used to score the canal morphology: presence and amount of smear layer; presence of organic and inorganic debris; surface profile. SEM assessment revealed that in the coronal and middle third the majority of canals shaped with NRT rotary system presented a clinically acceptable surface. The apical third presented a higher amount of smear layer and dentinal debris instead, compared to the coronal and middle third. NRT files demonstrated that they provided good instrumentation of the coronal and middle third, while being unable to obtain a defects-free surface in the apical third.

A comparative scanning electron microscopy evaluation of smear layer removal with apple vinegar and sodium hypochlorite associated with EDTA

ObjectiveThe purpose of this study was to evaluate by scanning electron microscopy (SEM) the removal of smear layer from the middle and apical root thirds after use of different irrigating solutions. Material and MethodsForty roots of permanent human teeth had their canals instrumented and were randomly assigned to 4 groups (n=10), according to the irrigating solution: apple vinegar (group A), apple vinegar finished with 17% ethylenediaminetetraacetic acid (EDTA) (group B), 1% sodium hypochlorite (NaOCl) finished with 17% EDTA (group C) and saline (group D - control). After chemomechanical preparation, the roots were cleaved longitudinally and their middle and apical thirds were examined by SEM at ×1,000 magnification. Two calibrated examiners (kappa=0.92) analyzed the SEM micrographs qualitatively attributing scores that indicated the efficacy of the solutions in removing the smear layer from the surface of the dentin tubules (1 - poor, 2 - good and 3 - excellent). Data from the control and experimental groups were analyzed by the Kruskal-Wallis and Dunn's test, while the Wilcoxon test was used to compare the middle and apical thirds of the canals within the same group (α=0.05). ResultsThe middle third presented less amount of smear layer than the apical third, regardless of the irrigant. There was statistically significant difference (p=0.0402) among the groups in the middle third. In the apical third, the apple vinegar/EDTA group showed the greatest removal of smear layer (p=0.0373). ConclusionApple vinegar associated or not with EDTA was effective in removing smear layer when used as an endodontic irrigant.

A scanning electron microscopic study of smear layer remaining following use of Greater Taper rotary instruments

The aim of this in vitro study was to evaluate the smear layer in the root canal following the use of Ni-Ti hand ProTaper, HERO shaper and Twisted rotary instruments. Fifteen freshly extracted single rooted human mandibular premolar teeth were selected. Crowns of all teeth were cut off at the cemento-enamel junction with a carborundum disc. The roots were then randomly divided into three groups of 5 samples each. The working length of all teeth was established by the insertion of an endodontic instrument into the canal until its tip is visible at the apical foramen and then subtracted by 0.5 mm. A sequential crown down technique was carried out in all the three groups as follows: Group-I- Specimens in this group were instrumented with ProTaper Ni-Ti hand instruments. Group-II- Specimens were instrumented with HERO shapers. Group-III - The specimens in this group were instrumented with Twisted rotary instruments. Irrigation was done with 3% NaOCl and 15% EDTA in all the three groups. Teeth were carefully split with hammer and chisel and stored in small labeled bottles containing normal saline until SEM evaluation. Results showed that when comparing ProTaper files, Twisted rotary instruments and HERO shaper instruments, HERO shaper series of rotary instruments showed maximum amount of smear layer followed by the Twisted rotary instruments. Hand instruments produced least amount of smear layer.

Evaluation of the smear layer and hybrid layer in noncarious and carious dentin prepared by air abrasion system and diamond tips

To analyze the smear layer and the hybrid layer in noncarious and carious dentin prepared by different cutting instruments and restored with composite resin. Cavities were randomly prepared in 160 specimens (noncarious and artificial carious dentin) by high-speed diamond tips (KG Sorensen 1013), air abrasion system (Prepstart, Danville Engineering), ultrasonic tip (CVDentus 8.3231-1), and ultrasonic tip associated with ultrasonic cavitation by water for 10 s. Half of the cavities in each group were conditioned with 37% phosphoric acid for 15 s. The amount of smear layer and dentinal tubules present were analyzed using scanning electron microscopy and graded from 0 to 3. Cavities were prepared in another 20 noncarious specimens and 20 carious specimens and restored with adhesive composite resin system. The restorations were hemisected longitudinally and analyzed using scanning electron microscopy to evaluate the hybrid layer and resinous prolongation characteristics, using scores ranging from 1 to 6. The data were statistically analyzed using Kruskal-Wallis and Dunn tests at 5% of significance level. There was evidence that the most efficient smear layer removal was the acid etching in the noncarious dentin and the water ultrasonic cavitation in the carious dentin. The hybrid layer formed on the noncarious and carious dentin prepared by the ultrasonic tip was more regular than in the specimens prepared by high-speed diamond tip, with many resinous prolongations. The ultrasonic tip seems to be a promising tool for carious dentin cavity preparation.

Ultrastructural morphologic evaluation of root canal walls prepared by two rotary nickel-titanium systems: a comparative study

To evaluate and compare the ultrastructural morphology, surface cleanliness, and roughness of root canal walls of extracted teeth after instrumentation with 2 different rotary nickel-titanium systems (ProTaper and NRT) when associated with the use of sodium hypochlorite and ethylenediaminetetraacetic acid combination as an irrigating regimen. A total of 40 freshly extracted single-rooted human mandibular premolars with fully developed apices and straight roots were selected. The roots were randomly divided into 2 experimental groups of 20 samples each according to the rotary system used in the preparation of the canals. In group I, canals were instrumented using the ProTaper file system; in group II, canals were prepared by the NRT file system. For each sample, an overall evaluation of the dentin surface along the whole length of the canal and a specific evaluation of the root dentin at the apical third was carried out regarding presence of debris, quality and amount of smear layer, and roughness using stereomicroscope and scanning electron microscope. Energy-dispersive spectroscopy was further used to detect nickel-titanium alloy remnants on the root dentinal surface of 2 randomly selected samples within each group. Statistical analysis showed no significant difference between the tested systems regarding debris and smear layer. The ProTaper system presented significantly smoother dentinal walls at the apical level than the NRT system. Alloy remnants were detected within the dentinal walls instrumented by both systems. Both systems produced relatively clean and debris-free dentin surfaces in the coronal thirds and to a lesser extent in the middle thirds. In contrast, these instruments were unable to produce a dentin surface free from smear layer and debris in the apical thirds. Smoother prepared walls could be achieved using ProTaper files. Remnants of nickel-titanium alloy were detected on the root dentin surface instrumented by both systems.

Assessment of Morphological Changes and Permeability of Apical Dentin Surfaces Induced by Nd:YAG Laser Irradiation through Retrograde Cavity Surfaces

The purpose of this in vitro study was to observe the morphological changes and apical dye penetration at apical dentin surfaces induced by Nd:YAG laser irradiation at different power settings with and without a laser initiator. Seventy five single rooted human maxillary anterior teeth were used. Following the establishment of the working lengths, the root canals were enlarged with step-back technique. The apex of each root was resected 3 mm perpendicular to its long axis. Standard Class I cavities of 2 mm depth and 2 mm width were prepared. The teeth were randomly divided into five groups with fifteen teeth in each. In Group 1, the retrograde cavity preparations were lased with Nd:YAG laser at 2 W and those in Group 2 preparations were lased with Nd:YAG laser at 3.2 W. In Group 3, the retrograde cavity surfaces were lased with Nd:YAG laser at 2 W following the application of India ink. Group 4 was lased with the same settings of Group 2 after an absorbent cotton point soaked with India ink was inserted into the cut dentinal surfaces and the inner walls of the apical preparations. Group 5 served as control. Five teeth from each group were examined using scanning electron microscopy (SEM). The amounts of smear layer, debris, and recrystalized dentin present were assessed and scored. Retrograde cavities of ten teeth from each group were filled with amalgam to examine apical dye penetration. The teeth were immersed in 2% basic fuscin and kept for 48 hours. Dye penetration was evaluated by stereomicroscope at a magnification of X10. The results showed the usage of India ink with Nd:YAG laser enhanced the amount of melting and recrystalization of dentin and the radiation and initiator increased the leakage.